In signal theory, the noise floor is the measure of the signal created from the sum of all the noise sources and unwanted signals within a measurement system.
In radio communication and electronics, this may include thermal noise, blackbody, and any other interfering signals. In a measurement system such as a seismograph, it may include nearby foot traffic or a nearby road. The noise floor limits the smallest measurement that can be taken with certainty since any measured amplitude can on average be no less than the noise floor.
A common way to lower the noise floor in electronics systems is to cool the system to reduce thermal noise, which is usually the major noise source. In special circumstances, the noise floor can also be artificially lowered with digital signal processing techniques.
